The present invention relates generally to integrated circuits (IC), and more particularly to a structure and method for fabricating a laterally configured thin film varistor surge protection device using low temperature sputtering techniques which do not damage IC device components contiguous to the varistor being fabricated.
High performance IC chips tend to suffer from transient voltages that can damage device components embedded within them. In particular, devices manufactured on thin film substrates are highly sensitive to electrostatic discharge (ESD). Conventional ESD protection devices are typically not robust enough for applications where high current transients are common. For example, silicon controlled rectifier (SCR) devices or generic transient voltage suppression (TVS) devices may not be suitable for ESD protection of radio frequency (RF) circuits manufactured on thin films, as thin film substrates are more sensitive to transient voltages compared to thick film substrates.
Varistors are non-ohmic devices that help protect sensitive IC components against such transient voltages. A varistor's resistance to the flow of electricity changes based on changes in the electric field. While a varistor remains non-conductive during normal operation voltages, its electrical resistance starts to decrease as voltage is raised and when voltage is excessively high, such as during surges, the varistor starts to conduct the significantly increased current, thus shunting the current away from sensitive IC components. Unlike SCR and TVS devices, varistors are stable at higher transient voltages, and at higher temperatures caused by such higher transient voltages.